public static <T> Message<?> messageWithHeaderEntry(String key, Matcher<T> valueMatcher) {
   return argThat(HeaderMatcher.<T>hasHeader(key, valueMatcher));
 }
 public static Message<?> messageWithHeaderEntries(Map<String, ?> entries) {
   return argThat(HeaderMatcher.hasAllHeaders(entries));
 }
 public static Message<?> messageWithHeaderKey(String key) {
   return argThat(HeaderMatcher.hasHeaderKey(key));
 }